Process of making protected metal



Sept. 3, 1929. F. M. CRAPO PROCESS OF MAKING PROTECTED METAL Filed March 25, 1925 INVENTOR.

ATTORNEY.

' Patented Sept. 3, 1929.

UNITED STATES PATENT OFFICE.

FREDERICK M. CRAPO, OF MUNCIE, INDIANA, ASSIGNOR TO INDIANA STEEL & WIRE COMPANY, OF MUNCIE, INDIANA, A CORPORATION OF INDIANA.

PROCESS OF MAKING PROTECTED METAL.

Application filed March 25, 1925. Serial No. 18,296.

It is the object of my invention to produce better zinc-coating of zinc-coated iron and low-carbon steel articles, especially wire; and to produce a zinc-coating which will adhere more firmly under deformation, such as twisting or bending.

In my Patent No. 1,501,887, granted July 15, 1924, I have described a zinc-coated article, specifically wire, and the method of producing it. This present invention embodies the generic invention covered in the aforesaid patent, but specifically relates to a modified way of producing such articles.

As explainedin such prior patent, difiiculty has been experienced in producing suitably adherent zinc-coatings on wire and other articles of iron and low-carbon steel. Inthe method specifically described in said patent, the article such as wire, which is subsequently to be zinc-coated is chemically heattreated by being passed through a bath of molten salts. The molten salts there described contain cyanide, and as the wire or other article passes through such molten salts it is annealed and cleaned, and receives in its surface such a permeative addition b chemical 'changethat a subsequently app ied zinc coating adheres more firmly under deforming stresses.

- In accordance with my present invention,

the wire or other article is suitably heattreated, as by being annealed, separately from its immersion in the bath of molten salts, either before or after such immersion but desirably before it. This has certain advantages: The heat treatment may be produced and controlled independently of the temperatune of the bath of molten salts in which the permeative addition by chemical change is produced in the surface of the article. The heat-treating temperature may thus be higher, if desired, than the temperature of the molten salts. A smaller quantity of molten salts may be used, and the time of immersion of the article in the molten salts may be decreased, so that the permeative addition by chemical change may be controlled independently of the annealing or other heat-treating operation. I prefer to obtain the heat-treatment in a gaseous medium, either by direct contact with hot gases from combustion or in a suitable gas-containing tube suitably heated; and may, if desired, use the heat of the same flames that are used for heat-treating to maintain the bath of molten salts in liquid condition at the desired temperature.

The accompanying drawing illustrates apparatus for carrying out my invention: Fig. 1 is a longitudinal sectional view showing diagrammatically an apparatus for annealing a wire, producing a permeative addition in its surface by chemical change, and zinccoating it, in accordance with my present inventlon, the wire here being annealed by direct exposure to hot gases from combustion, and the heat treatment here preceding the producing of the permeative addition; Fig. 2 is an enlarged section showing the bath of molten salts floating on and confined to a portion of the surface of a bath of molten lead, with the wire passing both downward and upward through the molten salts; Fig. 3 shows a modification of the salt-bath arrangement, so that the wire passes downward through the molten lead and only upward through the bath of molten salts and Fig. 4

shows further modifications, in which the wire is annealed in a tube-type annealing furnace, so that the wire is not in direct contact with combustion gases, the annealed wire passing through a bath of molten salts which is held directly in a container instead of being floated on a bath of molten lead as in Figs. 1, 2, and 3, and the wire passes throu h themolten salts before it passes through t e annealing furnace.

I have illustrated my invention in connection with the treatment of wire, in a continuous process; but my invention in its broader aspect is not limited either to the treatment of wire or to the continuous process. More- 7 over, the wire may be at any stage of its man-' ufacture, from the rod down to the wire at its final gage; because the permeative addition by chemical change will persist through further operations on the wire, such as subsequent reductions to smaller gage.

The wire 10, at whatever gage it is to be treated, from the rod-size down, is passed through a suitable heat treatment, as in an annealing furnace 11, which is shown as being heated by suitable fuel supplied through a burner 12. The hot gases from combustion may play directly on the wire 10 as the latter passes through the annealing furnace, as is illustrated in Fig. 1; or the wire 10 may be passed through a suitable tube 15 of a tubetype annealing furnace, as indicated in Fig.-

4, with the wire kept from direct contact with the combustion ases and merely subjected to heat transmitte to it throu h the tube 15 and the gas present in such tu e. The gas in said tube may be of any desired character.

In addition to its heat treatment, and as a separate step, the wire is passed througlra bath of molten salts, in which it receives m its surface such a permeative addition by chemical change that a subsequently applled zinc-coating will better adhere. These molten salts are desirably of the character set forth in my aforesaid patent, such as any commer cial cyanide mixture; and the cyanide WlllCh they contain acts to produce in the surface of the wire the permeative addition by chem cal change above referred to. I believe this permeative addition includes superficial car- 7 bonization of the iron-base wire, thus increasing the carbon content of the wire at the surface thereof with relation to that in themterior; but this superficial carbonization of the wire may not be the only permeative addltion by chemical change that occurs, and may not be the only change that occurs at the surface. I

The wire may pass through the bath of molten salts either before or after it receives its heat treatment, as in the annealing'fu'rnace. I deem it preferable to have the wire receive its heat treatment first and then to bewire is. shownv as being passed first through the bath of molten salts and then through an annealing furnace.

The bath of molten salts may take several.

different forms. It may take the form of a simple container 20, containing the molten Y salts 21, as is shown in Fig. 4. With this simple form, the wire 10 merely passes down into the molten salts 21, below a sinker 22 therein, and then upward out of the molten salts. As already stated, the passage of the wire through the annealing furnace may be either before or after this passage through the molten salts-'21.

It is difficult, however, to hold the molten salts 21 directl in a container 20; because of t the action of t id cyanide on the metal of the container. ,Theiefore, in place of puttingthe salts 21 directly in a container, I deem it better to use an arrangement in which the cyanide-bearing salts are kept out of contact with the container itself. Such an arrangement per se is set"=.forth and claimed in the co-(pending application of William Baylis an myself, Serial No, 707,869, filed April 21, 1924. With ,such an a rangement, I provide a container 25 which contains molten lead 26, into which dips a band or ring 27 which contains within it the molten salts 28 which salts float on the lead 26 and are co fined to a definite part of the surface of the ead and withheld from contact with the container 25 by the band or ring 27, which may be su ported in any suitable manner, as explaine in the aforesaid Crago and Baylis application. The wire 10 may 0 passed both downward and upward through such salts, beneath a sinker 22,. as indicated in Figs. 1 and 2; with the sinker 22, if desired, sufficiently lowso that it is wholly in the lead 26, though that is not necessary. Or, if desired, the MN 10 may be passed only in one direction through the molten salts and in the other through the molten lead for instance, as shown in Fig. 3,

downward through the molten lead 26 outside of the band or ring 27 then below the sinker 22, and then upward through the molten salts 28 within the band or ring 27. "The wire is desirabl held from contact with the air between tie annealing furnace and the treat- Y 2, and 3 the wire may ass through the annealing furnace either be ore or after it has passed through the molten salts, though in these figures it, is indicated as passing through the annealing furnace before it passes through the molten salts.

The lead-container 25 and the salts-container 20 are conveniently arranged close to the annealing furnace 1 1, in position to be heated by the same source of heat,"such as the flame from the burner 12, .as is indicated in Figs. 1, 2, and 4. However, when it is desired to control the temperature of the heat independently of that of the bath of molten salts,

the bath of molten salts may be heated from a separate source from the source which heats the annealing furnace, asby hflViZIBI g a sepa-y 1g. 3.. "i When the lead 26 is used, the heat of the rate burner 36, as is indicated in flame from the burner 12 or 36 melts the lead 26, and the heat is transmitted through the lead 26 to the salts 28 to keep such salts also molten.

With any of the arrangements shown in Figs. 2, 3, and 4, the wire 10 is passed through the furnace 11, and heat-treated, as by being annealed, in such passage; and is separately passed through a bath of molten salts in.

which it receives in its surface a permeative addition by chemical change.v The temperature in the furnace 11 should'besufiicient to produce the desired annealing, The temperature of the molten salts 21 or 28 is main tained somewhat above the melting point of such salts, advantageousl between 1200 and 1350 F.; and where the lead bath 26 is used, that is desirably maintained between 1275 and 1375 F. When the lead is used, it is usually desirable to cover it with a pulv'erized hard-coal or charcoal layer 35, which serves both to prevent heat loss by radiation and to lessen oxidation of the lead.

' furnace, it may or may not receive further mechanical working, as by' being passed through additional size-reducing dies in the" case of wire. For simplicity of illustration, no such further mechanical operatlons on the wire are shown, and the wire after passing from the bath of molten salts and the annealing furnace is immediately prepared forzinc-coating, and is then zinc coated.

This may be done in various ways. For simplicity I have shown the wire as being passed through a bath 30 of water for removing any adhering salts; then through a fluxing bath 31, of any suitable flux, such as hydrochloric acid or zinc chloride; then over a hot plate 32 for making certain that the wire will be sufficiently dried; and then through a bath 33 of molten zinc, in which the wire takes its zinc-coating. From the zinc-coating bath 33, the wire passes to the winding reel 34. In the zinc-coating of wire, I prefer to do it by this ordinary galvanizing process of passing the wire through molten zinc, although my invention is not limited to this hot-galvanizing process. When the zinc coating is obtained by passing the wire through a bath of molten zinc, such bath is advantageously maintained at about 840 to 900 F., in any convenient way; although that temperature may be varied in the judgment of the operator.

In the case of Wire of various sizes, and

' rods, the operations above described or such of them as are performed are desirably all produced in a continuous process, with the Wire moving continuously in the direction of thearrows. This is found possible because of the extremely short time in which it is necessary. for the wire to remain in contact with the salts 21 or 28; for there will be sufficient action of the hot salts on the hot wire in a very few secondssometimes in one second or even less-to produce a sufficient permeative addition by chemical action to give a greatly improved zinc-coating when the zinc-coating is subsequently applied.

I claim as my invention:

1. The process of zinc-coating an iron or low-carbon steel article, which consists in heat-treating the article at a temperature sufficiently high to produce annealing, separately immersing the article in a carbonizing bath of'molten salts, and subsequently apply-' ing a zinc coating to the article.

2. The process of zinc-coating an iron or low-carbon steel article, comprising heattreating such article in a gaseous medium at a temperature sufiiciently high to produce annealing, separately immersing the article in a carbonizing bath of molten salts, and subsequently applying a zinc coating.

'3. The process of zinc-coating an iron or low-carbon steel article, which consists in heat-treating the article in direct contact with gases of combustion at a temperature sufiiciently high to produce. annealing, subsequently immersing the article in a carbonizing bath of molten salts, and subsequently applying a zinc coating.

4. The method of zinc-coating iron or lowcarbon steel wire, comprising raising the wire to a heat-treating temperature sufficiently high to produce annealing, subsequently and before the -Wire has cooled from its heat treatment passing the wire through a bath of carbonizing salts, and subsequently zinc-coating such wire.

5. The method of zinc-coating iron or lowcarbon steel wire, comprising passing such wire through gas sufficiently hot to raise the wire to heat-treating temperature sufficiently high to produce annealing, subsequently and before the wire has cooled from its heat treatment passing the wire through a bath of carbonizing salts, and subsequently zinccoating such wire.

6. The method of zinc-coating iron or lowcarbon steel wire, comprising passing such wire through gases of combustion sufliciently hot to raise the wire to heat-treating temperature. sufliciently high to produce annealing, subsequently and before the wire has cooled from its heat treatment passing the wire through a bath of carbonizing salts, and subsequently zinc-coating such wire.

7. The method of zinc-coating iron or lowcarbon steel wire, comprising raising the wire to a heat-treating temperature sufli ciently high to produce annealing, subsequently passing the wire through a bath of carbonizing salts, and subsequently zinccoating such wire.

8. The method of zinc-coating iron or low carbon steel wire, comprising passing such wire through gas sufficiently hot to raise the wire to heat-treating temperature sufficiently high to produce annealing, subsequently passing the wire through a bath of carbonizing salts, and subsequently zinc-coating such wire.

9. The method of zinc-coating iron or lowcarbon steel wire, comprising passin such wire through gases of combustion su ciently hot to raise the wire to heat-treating temperature sufficiently high to produce annealing, subsequently passmg the wire through a bath of carbonizing salts, and subsequently zinc-coating such wire.

' 10. The process of zinc-coatingan iron or low-carbon steelarticle, comprising raising the temperature of the article to heat-treating temperature sufiiciently high to produce annealing, subsequently groducing such a permeative addition by c emical change in the surface of the article that a subsequently applied zinc coating will better adhere thereto, and subsequently applying such a zinc-coating.

The process of zinc-coating iron and low-carbon steel wire, comprising heatingadhere to such surface, and subsequently ap-' plying a zinc coating to such surface.

12. The process of Zinc-coatin iron and low-carbon steel wire, comprising eating the Wire to heat-treating temperature sufliciently high to'produce annealing, subsequently producing \such a permeative addition by .chemical change in the surface of the wire that a subsequently applied zinc coating will better adhere to such surface, and subsequently applying a zinc coating to such surace.

13. The process of zinc-coating an iron or low-carbon steel article, which consists in heat-treating the article at a temperature sufliciently high .to produce annealing, subsequently and separately immersing the article in a carbonlzing bath of molten salts, and subsequently applying a zinc-coating to the article.

14. The process of zinc-coating an iron or low-carbon steel article, which consists in heat-treating the article in direct contact with gases of .combustionat a temperature sufliciently high to produce annealing, sep-- aratelg immersing the article in a carbonizing thof molten salts, and subsequently ap lyinga zinc-coating.

n witness whereof, I have hereunto set my hand at Munice, Indiana, this 21st day of March, A. D. one thousand nine hundred and twenty five.

FREDERICK M. ORAPO. 

